I don't know that this is the best method, to simply hide the captcha rather than terminating the session. The plugin does give pretty error messages, but there seems like there should be some better way.

Assistance on LimeSurvey forum and LimeSurvey core development are on my free time.
I'm not a LimeSurvey GmbH member,
professional service on demand
(or search sondages pro).
An error happen ? Before make a new topic : remind the
Debug mode
.